Organic el display apparatus and method of manufacturing organic el display apparatus

ABSTRACT

The present invention is equipped with: a substrate (10) that has a surface upon which a drive circuit containing a TFT (20) is formed; a planarizing layer (30) that makes the surface of the substrate (10) planar by covering the drive circuit; and an organic light emitting element (40) that is provided with a first electrode (41) formed upon the surface of the planarization film and connected to the drive circuit, an organic light emitting layer (43) formed upon the first electrode, and a second electrode (44) formed upon the organic light emitting layer. In addition, the planarizing layer (30) includes a first inorganic insulating layer (31) and an organic insulating layer (32) that are layered upon the drive circuit, and the surface of the organic insulating layer (32) is formed with an arithmetic mean roughness Ra of no more than 50 nm.

TECHNICAL FIELD

The present invention relates to an organic EL display apparatus and amethod of manufacturing an organic EL display apparatus.

BACKGROUND ART

In recent years, there is a tendency to adopt an organic EL displayapparatus for a large sized television and a mobile apparatus. Theorganic EL display apparatus is configured by a drive circuit beingformed on an insulating substrate, the drive circuit using a thin filmtransistor (below also called a TFT) as an active element such as aswitching element or a drive element in each pixel region, and anorganic light emitting element for each pixel being formed on the drivecircuit so as to connect to the TFT. The organic EL display apparatuscan be categorized into a top emission type in which a front surface ofthe light emitting element is a display surface and a bottom emissiontype in which a rear surface of the insulating substrate is a displaysurface. In the top emission type, the previously-described drivecircuit can be formed below the display region of the organic lightemitting element, not out of the display region of the organic lightemitting element. On the other hand, in the bottom emission type, thedrive circuit is formed at the peripheral edge of the display region.Therefore, for a small sized organic EL display apparatus such as amobile apparatus having a small space to form the drive circuit, the topemission type, or in other words, a configuration such that the drivecircuit such as the TFT is formed below almost the entire surface of thedisplay region is often used. On the other hand, the bottom emissiontype is suitable for the large sized television having some space tospare between pixels.

When the drive circuit including TFT is formed, the surface thereofbecomes uneven. As the organic light emitting element is formed thereon,a planarizing layer is formed by covering over the drive circuit with aresin material. In this way, the surface is planarized. In the priorart, this planarizing layer is obtained by, forming a first inorganicinsulating layer to be a barrier layer after the TFT is formed, andforming a contact hole for connecting the previously described organiclight emitting element and the TFT by a photolithography process, andforming a photosensitive organic insulating layer on the first inorganicinsulating layer being formed with the contact hole, and forming acontact hole by photolithography process and wet development. In thisway, the organic insulating layer is formed to planarize unevenness ofthe surface due to forming of the TFT.

Patent document 1 discloses a TFT and a manufacturing method thereof toachieve both a small occupation area and excellent transistorcharacteristics, the TFT and the manufacturing method being suitable fora switching element for each pixel of an active matrix type displayapparatus. Therein, multi-layer TFTs are integrally formed vertically byforming Is having the same configuration via an interlayer insulatinglayer whose surface unevenness is made to be no more than 20 nm by a CMPprocess. In other words, in forming multi-layer fine TFTs, the planarityof the surface of the interlayer insulating layer between themulti-layer TFTs requires to be made in no more than 20 nm to deal witha small depth of focus. Therefore, this planarizing is different from anintent to planarize an organic insulating layer which is an under layerfor an organic light emitting device over the TFT.

PRIOR ART DOCUMENT

Patent Document

-   Patent Document 1: JP 2017-011173 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

On the other hand, in a case of visually recognizing an organic ELdisplay apparatus, depending on a pixel, color non-uniformity orluminance non-uniformity can occur, causing the visual recognitioncharacteristics to be reduced. As a result of intensive studies on thecause that color non-uniformity or luminance non-uniformity occurs, thepresent inventor has found that it is caused by a lack of planarity ofthe surface of the organic light emitting layer. In other words, asdescribed previously, the organic light emitting element is formed on aplanarizing layer which is formed on a TFT constituting a drive circuitor the like, and planarizes the surface of the TFT. The surface of anorganic insulating layer constituting the planarizing layer is generallyplanar, so that conventionally it was believed to have no problems.However, as a result of the present inventor having made intensivestudies, it was found that the surface of the organic insulating layerwas found to be approximately 100 nm to 300 nm in arithmetic averageroughness Ra even when using a non-photosensitive resin. With aphotosensitive resin being generally used conventionally, it was foundthat further unevenness occurred, and that forming an electrode of theorganic light emitting element and the organic light emitting layer onthe surface causes the same degree of surface roughness also for thesurface of the organic light emitting layer. When unevenness occurs onthe surface of the organic light emitting layer, the orientation oflight travelling, when viewed microscopically, becomes in a variousdirection. Therefore, it was found that, when the display screen isviewed from the front surface, light travelling in a slanted directionis difficult to be visually recognized, causing color non-uniformityand/or luminance non-uniformity.

There is a problem that display definition decreases when displaynon-uniformity caused by luminance non-uniformity and/or colornon-uniformity as described previously occurs, even in a case that thereis no obvious display defect such as a non-lighted region, analways-lighted region, or a bright line in a display screen of a displayapparatus.

Moreover, in a conventional organic light emitting element, it ispracticed to increase a light emitting output by making a microcavity byproviding a layer with a large reflectance on a surface of the organiclight emitting layer. In this case, there occurs unevenness on thesurface of the organic light emitting layer, and thereby, unevenness isformed even on the reflective layer, so that a light from the organiclight emitting layer reflects irregularly, and it is not possible toeffect a complete resonator. Therefore, there is a problem that, it isnot possible to obtain an increase in output.

On the other hand, in the present invention, as it is not an object tomanufacture a multi-layer fine TFT, it is not required to form a strictsurface planarity at no more than 20 nm as disclosed in the previouslydescribed Patent Document 1. It suffices to have such a planarity degreethat light emitted from the organic light emitting layer enterssubstantially to the front surface of the display with a peak in aboutthe center.

An object of the present invention being made in view of suchcircumstances as described above is to provide an organic EL displayapparatus and a manufacturing method thereof in which colornon-uniformity and/or luminance non-uniformity of an organic EL displayapparatus is suppressed to improve display definition.

Means to Solve the Problem

An organic EL display apparatus according to one embodiment of thepresent invention comprises: a substrate having a surface on which adrive circuit comprising a thin film transistor is formed, a planarizinglayer to planarize the surface of the substrate by covering the drivecircuit, and an organic light emitting element, the organic lightemitting element comprising a first electrode being formed on a surfaceof the planarizing layer and connected to the drive circuit, an organiclight emitting layer being formed on the first electrode, and a secondelectrode being formed on the organic light emitting layer, wherein theplanarizing layer comprises a first inorganic insulating layer and anorganic insulating layer, the first inorganic insulating layer and theorganic insulating layer being deposited on the drive circuit, andwherein a surface of the organic insulating layer is formed to less thanor equal to 50 nm in arithmetic plane roughness Ra.

A method of manufacturing an organic EL display apparatus according toanother embodiment of the present invention comprises: forming a drivecircuit on a substrate, the drive circuit comprising a thin filmtransistor (TFT); forming, on a surface of the drive circuit, a firstinorganic insulating layer and an organic insulating layer; polishing asurface of the organic insulating layer by chemical mechanical polishing(CMP); forming a contact hole in the organic insulating layer and thefirst inorganic insulating layer, the contact hole to reach the TFT;embedding a metal at an interior of the contact hole and forming a firstelectrode at a given region; forming an organic light emitting layer onthe first electrode; and forming a second electrode on the organic lightemitting layer.

Effects of the Invention

According to the embodiment of the present invention, the organicinsulating layer is formed on an uneven surface of the drive circuitcomprising a TFT and the surface of the organic insulating layer ispolished using CMP to cause the surface to be planarized such that theplanarity of the surface is brought to less than or equal to 50 nm inarithmetic average roughness Ra. As a result, light travelling in aslanted direction, when viewed microscopically, is substantiallysuppressed, causing an occurrence of color non-uniformity and/orluminance non-uniformity to be suppressed and the display quality of theorganic EL display apparatus to be substantially increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of an organic EL display apparatusaccording to one embodiment of the present invention.

FIG. 2A shows a flowchart of a process of manufacturing an organic ELdisplay apparatus according to Example 1, the Example 1 being without asecond inorganic insulating layer in FIG. 1.

FIG. 2B shows a flowchart explaining the process of FIG. 2A in furtherdetail.

FIG. 3A shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3B shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3C shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3D shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3E shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3F shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, the Example 1 beingwithout the second inorganic insulating layer in FIG. 1.

FIG. 3G shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus according to Example 1, which is withoutthe second inorganic insulating layer in FIG. 1.

FIG. 4A shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus in FIG. 1 according to Example 2.

FIG. 4B shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus in FIG. 1 according to Example 2.

FIG. 4C shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus in FIG. 1 according to Example 2.

FIG. 4D shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus in FIG. 1 according to Example 2.

FIG. 4E shows a cross-sectional view of the process of manufacturing theorganic EL display apparatus in FIG. 1 according to Example 2.

EMBODIMENT FOR CARRYING OUT THE INVENTION

An organic EL display apparatus being one embodiment of the presentinvention will be described below with reference to the drawings. FIG. 1schematically shows a cross-sectional view of what corresponds to onepixel (while it, more strictly, refers to sub-pixels of red, green, andblue in one pixel), the present specification can also include thesesub-pixels to refer thereto.

An organic EL display apparatus according to one embodiment of thepresent invention, as shown in an explanatory view of a cross sectionthereof, comprises: a substrate 10 having a surface on which a drivecircuit comprising a TFT 20 is formed, a planarizing layer 30 toplanarize the surface of the substrate 10 by covering the drive circuit,and an organic light emitting element 40, the organic light emittingelement 40 comprising a first electrode 41 being formed on a surface ofthe planarizing layer 30 and connected to the drive circuit, an organiclight emitting layer 43 being formed on the first electrode 41, and asecond electrode 44 being formed on the organic light emitting layer 43.Then, the planarizing layer 30 comprises a first inorganic insulatinglayer 31 and an organic insulating layer 32, the first inorganicinsulating layer 31 and the organic insulating layer 32 being depositedon the drive circuit, and the surface of the organic insulating layer 32is formed to less than or equal to 50 nm in an arithmetic planeroughness Ra. Then, the organic light emitting layer 43 is formed suchthat it avoids a portion being immediately above a contact hole 30 a.

In other words, the organic EL display apparatus according to thepresent embodiment has one feature that the surface of the substrate 10being uneven by the drive circuit being formed thereon is formed to theplanarity being less than or equal to 50 nm in the arithmetic planeroughness Ra by forming the planarizing layer 30 through a deposition ofthe inorganic insulating layer 31 and the organic insulating layer 32and further by polishing the surface of the organic insulating layer 32using CMP method. The planarizing layer 30 can be formed by furtherforming a second inorganic insulating layer 33 on the surface of theorganic insulating layer 32, and, in the example shown in FIG. 1, thesecond inorganic insulating layer 33 is also formed. Moreover, theorganic EL display apparatus according to the present embodiment hasanother feature that the organic light emitting layer 43 is formed in aregion being not immediately above the contact hole 30 a to connect thedrive circuit and the first electrode 41.

As described previously, as a result of the present inventors havingcarried out intensive studies on the cause that color non-uniformity orluminance non-uniformity of the organic EL display apparatus occurs, itwas found that there is unevenness on the surface of the organic lightemitting layer 43 of the organic light emitting element 40, the surfaceof the organic light emitting layer 43 is not completely planar but hasan inclined portion when viewed microscopically, and, when inclined, thenormal direction of the surface of the organic light emitting layer 43is inclined relative to the normal direction of the display surface.Then, in a case of visually recognizing from a direction perpendicularto the display surface, it becomes difficult to recognize light of apixel for which light emitted travels in a slanted direction, causingdeterioration in luminance or a color of mixed colors to change. Inother words, light emitted having maximum luminance in the normaldirection thereof will have luminance thereof decreasing as it isinclined relative to the normal direction. With a small-sized displayapparatus such as a smartphone, the size of this sub-pixel is very smallwith one side of a few tens of μm. Therefore, even with slightunevenness, light emitted toward the front becomes very weak for asub-pixel having unevenness on the surface of the organic light emittinglayer 43.

Conventionally, as the countermeasure for such color non-uniformityand/or luminance non-uniformity, incorporating a TFT at the externaledge of the display panel and, using a circuit, adjusting luminance of apixel having color non-uniformity and/or luminance non-uniformity in aninspection after forming into a product are carrier out. Therefore,there is also a problem of a drive circuit becoming complex.

According to one embodiment, as the present inventor has found the causeof color non-uniformity and/or luminance non-uniformity as describedpreviously, and found that the color non-uniformity and/or luminancenon-uniformity almost does not occur by bringing the planarity of thesurface of the planarizing layer 30 to be a base of the light emittingelement to less than or equal to 50 nm and forming the organic lightemitting layer 43 while avoiding a portion being immediately above thecontact hole 30 a in order to improve the planarity of the surface ofthe above-mentioned organic light emitting layer 43. The presentinventor has found that, while the smaller the surface roughness themore preferable, bringing the planarity to less than or equal to 20 nmas shown in previously-described Patent Document 1 is not required, sothat the color non-uniformity or luminance non-uniformity almost doesnot occur even when the arithmetic average roughness Ra is greater thanor equal to 20 nm. In other words, while the smaller the surfaceroughness the more preferable, so that no lower limit is set, but thepolishing work gets cumbersome to decrease the surface roughness, sothat bringing the surface roughness to 20 nm or more and less than orequal to 50 nm is preferable.

More specifically, with the conventional method, with respect to theabove-mentioned planarizing layer, an inorganic barrier layer is formed,then a contact hole is formed by dry etching, and an organic insulatinglayer (a photosensitive resin) is formed thereon to form a contact holeby wet etching. In other words, as described previously, there wasbelieved to be no problem as the surface is planarized since the organicinsulating layer is formed by applying a liquid resin, the surface isplanarized. However, the planarity of the surface of the above-mentionedorganic insulating layer is approximately 100 nm to 300 nm in thearithmetic average roughness Ra even when a non-photosensitive resin isused, the above-mentioned planarity is greater than the above with aphotosensitive resin, and the present inventor has found thatplanarizing to such a degree is not sufficient. In this case, when thephotosensitive resin is used, the surface roughness further increasesdue to the influence of a photopolymerization initiator to be mixedthereinto. Then, as described previously, it has been found that anoccurrence of color non-uniformity and/or luminance non-uniformity canbe entirely suppressed by bringing the surface roughness to greater thanor equal to 20 nm and less than or equal to 50 nm in the arithmeticaverage roughness Ra through polishing the surface of the organicinsulating layer 32 using CMP. In other words, while it is not requiredto bring the planarity to less than or equal to 20 nm as disclosed inthe previously-described Patent Document 1, it is required to bring theplanarity to less than or equal to approximately 50 nm.

(Structure of Organic EL Display Apparatus)

The organic EL display apparatus shown in FIG. 1 and the method ofmanufacturing thereof are specifically described below.

The substrate 10 needs to transmit light emitted in the organic lightemitting layer 43 in a case of a bottom emission type in which a displayimage is visually recognized with the substrate surface as a displaysurface, so that an insulating substrate with a light-transmittingmaterial is used. More specifically, a glass substrate, or a resin filmsuch as polyimide is used. Using the resin film makes it possible tomake the organic EL display apparatus flexible and to bond it to acurved surface.

In a case that the substrate 10 is a resin film such as polyimide, thesurface thereof is not crystalline and it is difficult to directly forma semiconductor layer on the surface, so that a base coat layer 11 isformed, although this is not required in a case that the substrate 10 isa glass substrate. As the base coat layer 11, a deposited body of SiO₂having a thickness of approximately 500 nm, SiN_(x) having a thicknessof approximately 50 nm, and SiO₂ having a thickness of approximately 250nm, for example, is formed.

A drive circuit comprising the TFT 20 is formed on the base coat layer11. While only a cathode wiring 27 is shown in FIG. 1, other gatewirings and signal wirings are also similarly formed. Then, the TFT 20is formed thereon. While only the TFT 20 to drive the light emittingelement 40 is shown in FIG. 1, other TFTs such as other switching TFTsare also similarly formed. In a case that the organic EL displayapparatus is the top emission type having a surface opposite to thesubstrate 10 as a display surface, the drive circuit can be formed overthe entire surface below the light emitting region of the organic lightemitting element 40. However, in a case of the bottom emission typehaving the substrate 10 end as the display surface, the TFT cannot beformed below the light emitting region of the organic light emittingelement 40. Therefore, it is necessary that the TFT be formed at theperipheral edge of a portion planarly overlapping the light emittingregion. In this case, as an inclined surface is formed at a borderingportion between the peripheral edge at which the surrounding TFT orwiring is formed and a region under the light emitting region in whichthe TFT is not formed, unevenness occurs at the peripheral edge of thelight emitting region, causing the display quality to deteriorate.Therefore, even with the bottom emission type, the same degree ofplanarity is needed. While a capacitor can also be formed for eachpixel, it has a large area and the thickness thereof is small, so thatit almost does not cause a fine unevenness even when it is formed belowthe light emitting region.

The TFT 20 comprises a semiconductor layer 21 comprising a source 21 s,a channel 21 c, and a drain 21 d; a gate insulating layer 22; a gateelectrode 23; an interlayer insulating layer 24; a source electrode 25;and a drain electrode 26. Specifically, a drive circuit comprising theTFT 20 is formed as follows. The gate insulating layer 22 comprises SiO₂having approximately 50 nm in thickness, while the gate electrode 23 isformed by patterning after forming a layer such as Mo havingapproximately 250 nm in thickness. Thereon the interlayer insulatinglayer 24 comprising an SiO₂ layer of approximately 300 nm in thicknessand an SiN_(x) layer of approximately 300 nm in thickness being formedon the gate electrode 23, and the source electrode 25 and the drainelectrode 26 being formed so as to be connected to the source 21 s andthe drain 21 d. Before the interlayer insulating layer 24 is formed, thecathode wiring 27 and the electrode connecting portion of the source 21s and the drain 21 d are doped with boron and leading to increasedconcentration (p⁺), and activated by annealing. More particularstructures will be described in particular examples of the belowdescribed manufacturing method. While the example shown in FIG. 1 showsa top gate structure in which the gate electrode 23 is formed at aportion opposing the substrate 10 of the semiconductor layer 21, thesame also applies to a bottom gate structure in which the gate electrode23 is formed on the substrate 10.

On the surface of the drive circuit comprising the TFT 20, a firstinorganic insulating layer 31 comprising SiN_(X) of approximately 200 nmin thickness as a barrier layer and an organic insulating layer 32comprising a polyimide or acrylic resin, for example, of approximately 2μm in thickness and the surface roughness is brought to less than orequal to 50 nm in the arithmetic average roughness Ra using CMP. Theabove-mentioned organic insulating layer can also be a photosensitiveorganic insulating layer into which is mixed a photopolymerizationinitiator. With respect to the photosensitive organic insulating layer,the organic insulating layer 32 is formed after forming the firstinorganic insulating layer 31 and the contact hole 30 a is formed byexposure and development using the photolithography process. In thiscase, the CMP can be carried out after the contact hole 30 a is formed.Even though the polishing agent for CMP gets into the contact hole 30 aat the time of CMP polishing the organic insulating layer 32, as thesize of the contact hole is much greater than (for example,approximately 50 times) the particle diameter of the polishing agent,the polishing agent can be removed by cleaning, so that no problemsoccur in particular. In a case that the organic insulating layer 32 isnon-photosensitive, the contact hole 30 a for the organic insulatinglayer 32 is formed collectively with that for the first inorganicinsulating layer 31. On this occasion, a contact hole 30 b to form asecond contact 45 to connect a cathode (a second electrode) of theorganic EL display apparatus to the cathode wiring 27 is also formed inthe planarizing layer 30 at the same time.

In the example shown in FIG. 1, the second inorganic insulating layer 33of approximately 400 nm in thickness, the second inorganic insulatinglayer 33 comprising SiN_(X), for example, is formed on the organicinsulating layer 32. The second inorganic insulating layer 33 beingformed is preferable in that corrosion of the organic insulating layerby the etchant can be prevented at the time of etching to form thecontact hole 30 a. Moreover, the inorganic insulating layer maintainsthe planarity of the base thereof as it is, so that there is no need topolish the inorganic insulating layer. The contact holes 30 a for thethree layers are formed by collectively etching the three layers afterforming the second inorganic insulating layer 33.

Then, a conductor layer comprising ITO, a metal such as Ag or APC, andITO, for example, is deposited by sputtering or the like to cause ametal such as Ag or the like to be embedded into the contact hole 30 a,and the first electrode (anode) 41 is formed by a deposited layer ofITO/Ag or APC/ITO in which the surface and the lowermost layer are ITOlayers and Ag or APC is interposed between the ITO layers, usingpatterning after a conductor layer of the same metal such as Ag or APCand ITO is formed on the surface of the organic insulating layer 32 orthe second inorganic insulating layer 33 (in a case that the secondinorganic insulating layer 33 is formed), or in other words, theplanarizing layer 30. While the first electrode 41 is formedcontinuously to the conductor layer being embedded into the contact hole30 a, it is formed by patterning it such that it is positioned on thesurface of the planarizing layer 30 whose surface is planarized,avoiding where a recess on the contact hole 30 a is likely to occur. Inthis way, the planarity of the surface of the first electrode 41 isbrought to the same degree of planarity as that of the surface of theplanarizing layer 30, and the surface of the organic light emittinglayer 43 on the first electrode 41 is also brought to the same degree ofplanarity.

The first electrode (anode) 41 preferably has a work function ofapproximately 5 eV, so that, in a case of the top emission type, theabove-described material is used. The ITO layer is formed to thethickness of approximately 10 nm, and the Ag or APC is formed to thethickness of approximately 100 nm. In a case of the bottom emissiontype, the ITO layer is formed to the thickness of approximately greaterthan or equal to 300 nm and less than or equal to 1 μm, for example. Aninsulating bank 42, being formed of an insulating material, to insulatethe anode from the cathode as well as to demarcate each pixel is formedat the peripheral edge of the above-mentioned first electrode 41, andthe organic light emitting layer 43 is deposited on the first electrode41 being surrounded by the insulating bank 42.

The organic light emitting layer 43 is deposited on the first electrode41 being exposed while being surrounded by the insulating bank 42. Whilethe organic light emitting layer 43 is shown as one layer in FIG. 1, itis formed as a plurality of layers with various materials beingdeposited. Moreover, as the organic light emitting layer 43 issusceptible to moisture and cannot be patterned after forming it on theentire surface, it is formed by selectively vapor depositing onto only arequired portion, using a mask, an organic material being evaporated orsublimed. Alternatively, the organic light emitting layer 43 can beformed by printing.

More specifically, as a layer to be in contact with the first electrode(anode electrode) 41, for example, a positive hole injection layer canbe provided, which comprises a material having a high compatibility withionization energy to improve the injectability of positive holes. Apositive hole transport layer allowing trapping of electrons into thelight emitting layer (as the energy barrier) as well as improving thestable transport of positive holes is formed by an amine-based material,for example, on the positive hole injection layer. Moreover, a lightemitting layer to be selected in accordance with the light emittingwavelength is formed thereon using Alga being doped with a red or greenorganic fluorescent material for red or green light emission, forexample. Moreover, a DSA-based organic material is used as a bluecolor-based material. On the other hand, for coloring using a colorfilter (not shown), all of the light emitting layers can be formed withthe same material without any doping. On the light emitting layer isfurther formed, using Alq₃, an electron transport layer capable ofstably transporting electrons as well as improving the electroninjectability. These layers, each having several tens of nm inthickness, are deposited to form deposited layers being the organiclight emitting layer 43. An electron injection layer capable ofimproving the electron injectability, such as LiF or Liq, can also beprovided between this organic light emitting layer 43 and the secondelectrode 44. While this is not an organic layer, it is comprised withinthe organic light emitting layer 43 in the present specification sinceit is to emit light by an organic layer.

As described previously, with respect to the light emitting layer of thedeposited organic light emitting layer 43, an organic material as amaterial according to each color of R, G, or B is not deposited, so thata color display apparatus can be provided using a color filter. In otherwords, the light emitting layer can be formed using the same organicmaterial and a luminescent color can be specified using the color filternot shown. Moreover, emphasizing the light emission performance, thepositive hole transport layer and the electron transport layer arepreferably deposited separately using a material suitable for the lightemitting layer. However, taking into account the material cost aspect,depositing can also be carried out using the same material being commonto two or three colors of R, G, and B.

After the whole deposited organic light emitting layer 43 comprising theelectron injection layer made of, for example, LiF is formed, the secondelectrode (for example, cathode) 44 is formed on the surface thereof.More specifically, the second electrode 44 is formed over the organiclight emitting layer 43. The second electrode (cathode) 44 iscontinuously formed to be common across all the pixels. The cathode 44is connected to the cathode wiring 27 via a first contact 28 formed inthe insulating layer 22 and the insulating layer 24 of the TFT 20 andthe second contact 45 formed in the planarizing layer 30. The secondelectrode 44 being formed by a light-transmitting material, for example,a thin film Mg—Ag eutectic layer, is susceptible to corrosion withmoisture, so that it is encapsulated with an encapsulation layer 46being provided on the surface thereof. The cathode material ispreferably a material whose work function is small, so that an alkalinemetal or an alkaline earth metal can be used. While Mg, whose workfunction is small at 3.6 eV, is preferable, it is active and not stable,so that it is co-deposited with approximately 10 mass % of Ag, whosework function is 4.25 eV. Al, whose work function is also small atapproximately 4.25 eV, can also be used as a cathode material with LiFbeing used as the under layer. Therefore, with the bottom emission type,Al can be formed thickly in this second electrode 44.

The encapsulation layer (TFE: Thin Film Encapsulation) 46, comprising aninorganic insulating layer such as SiN_(X) or SiO₂, for example, can beformed with one deposited layer or with at least two deposited layers.For example, it is formed with a deposited layer having the thickness ofone layer of approximately from 0.1 μm to 0.5 μm, for example, and,preferably, with deposited layers of approximately two layers. Thisencapsulation layer 46 is preferably formed in a plurality of layers,each with different materials. Even when pin holes are created by theencapsulation layer 46 being formed with a plurality of layers, the pinholes seldom match completely in the plurality of layers, so that theencapsulation layer 46 is completely shielded from outer air. Asdescribed previously, this encapsulation layer 46 is formed so as tocompletely encapsulate the organic light emitting layer 43 and thesecond electrode 44. The encapsulation layer 46 can also comprise anorganic insulating material in between two inorganic insulating layers.

Method of Manufacturing an Organic EL Display Apparatus Example 1

A method of manufacturing an organic EL display apparatus without asecond inorganic insulating layer 33 of an organic EL display apparatusshown in FIG. 1 is explained with reference to flowcharts in FIGS. 2Aand 2B and views of the process of manufacturing in FIGS. 3A to 3G.

First, as shown in FIG. 3A, a drive circuit comprising a TFT 20 isformed on a substrate 10 (51 in FIG. 2A). Specifically, a base coatlayer 11 is formed on the substrate 10 as shown in the flowchart in FIG.2B (S11). The base coat layer 11 is formed, using plasma CVD, forexample, by depositing an underlayer comprising an SiO₂ layer having athickness of approximately 500 nm, and an SiN_(X) layer having athickness of approximately 50 nm on the SiO₂ layer, and by furtherdepositing, as an overlayer, an SiO₂ layer having a thickness ofapproximately 250 nm.

Thereafter, a semiconductor layer 21 comprising an amorphous silicon(a-Si) layer is formed on the base coat layer 11 using reduced pressureplasma CVD, for example (S12). Thereafter, conversion into polysilicon(LTPS: low temperature polysilicon) is carried out by carrying out anannealing process for approximately 45 minutes under the temperature ofapproximately 450 degrees Celsius under a nitrogen atmosphere, forexample (S13).

Next, a resist mask is formed using a photolithography process, thesemiconductor layer 21 is patterned by dry etching, and a portion of thesemiconductor layer 21 to be the TFT 20 and a wiring such as a cathodewiring 27 are formed (S14). Thereafter, a gate insulating layer 22 isformed (S15). The gate insulating layer 22 is formed by forming SiO₂ toa thickness of approximately 50 nm using plasma CVD.

Thereafter, a gate electrode 23 is formed by forming a metal layer ofmolybdenum (Mo) having a thickness of approximately 250 nm usingsputtering, for example, and patterning the Mo layer by carrying out dryetching after forming a resist mask using a photolithography process(S16).

Thereafter, a source 21 s and a drain 21 d are formed in thesemiconductor layer 21. More specifically, after boron ions (B⁺) aredoped, for example, the doped boron ions are activated by carrying outan annealing process for approximately one hour at the temperature ofapproximately 400 degrees Celsius, allowing the source 21 s and thedrain 21 d to be formed with the resistance thereof being reduced (S17).As the gate electrode 23 serves as a mask, the boron ions are notimplanted into a channel 21 c, but are implanted only into the source 21s and the drain 21 d, allowing the resistance of the source 21 s and thedrain 21 d to be reduced.

Thereafter, an interlayer insulating layer 24 is formed on the entiresurface and contact holes 24 a to expose a part of the source 21 s andthe drain 21 d are formed (S18). The interlayer insulating layer 24 isformed by forming a deposited layer of an underlayer comprising mainlySiO₂ and having a thickness of approximately 300 nm, and an overlayercomprising mainly SiN_(X) and having a thickness of approximately 300nm, using reduced pressure plasma CVD, for example. The contact hole 24a is formed by forming a mask through formation of a resist layer and aphotolithography process, and carrying out wet etching.

Thereafter, a metal material is deposited, so that a metal is embeddedinto the contact hole 24 a and a metal layer of a source electrode 25and a drain electrode 26 is formed on the surface of the interlayerinsulating layer 24 (S19). The source electrode 25 and the drainelectrode 26 are formed by, using sputtering, for example, depositing aTi layer having a thickness of approximately 300 nm and an Al layerhaving a thickness of approximately 300 nm and further depositingthereon Ti having a thickness of approximately 100 nm. Patterning ametal layer being formed on the interlayer insulating layer 24 using thephotolithography process and wet etching as described previously allowsthe source electrode 25 and the drain electrode 26 being connected tothe source 21 s and the drain 21 d, respectively, of the semiconductorlayer 21 to be formed. A first contact 28 connected to the cathodewiring 27 is formed using entirely the same method with the sameprocesses as forming this source electrode 25 and drain electrode 26.

Using the above-described processes, a drive circuit comprising a TFT 20of the top gate type using a top contact type LTPS, or, in other words,a portion called a backplane is formed. However, the TFT 20 is notlimited to this structure, so that it can be used with the top gate typeusing the bottom contact type structure, the bottom gate type using thetop contact type structure, or the bottom gate type using the bottomcontact type structure.

Thereafter, as shown in FIG. 3B, a first inorganic insulating layer 31and an organic insulating layer 32 are formed on the surface of thedrive circuit (S2 back in FIG. 2A). The first inorganic insulating layer31 is formed by forming a layer of SiN_(X) having a thickness ofapproximately 200 nm using plasma CVD, for example. The first inorganicinsulating layer 31 functions as a barrier layer to prevent a componentof the organic insulating layer 32 from penetrating toward the TFT 20.Moreover, the organic insulating layer 32 is intended to fill up aportion of unevenness present on the surface due to the formation of theTFT 20. The surface of the organic insulating layer 32 is easilyplanarized by applying a liquid-like resin. While methods of applyingcomprise a slit coat method or a spin coat method, a slit and spin coatmethod combining both can be used. This organic insulating layer 32 isformed so as to have the thickness of approximately 2 μm, so that apolyimide resin or an acrylic resin can be used, for example. It can bea photosensitive resin in which a photo polymerization initiator ismixed into these resins, an example of the resin mixed with the photopolymerization initiator will be described below. However, anon-photosensitive resin not containing the photo polymerizationinitiator is preferable since it is high in purity and, even more, thesurface smoothness thereof is high. More particularly, an acrylic resinis preferable.

Next, as shown in FIG. 3C, the surface of the organic insulating layer32 is polished by CMP (S3). As the liquid resin is applied and dried toobtain the organic insulating layer 32, the surface of the organicinsulating layer 32 is easily planarized and, as described previously,the surface thereof is formed to approximately 100 nm to 300 nm inarithmetic average surface roughness Ra. However, the present inventorhas found that, as described previously, the planarity of theplanarising layer obtained by only applying the liquid resin and dryingcauses color non-uniformity and/or luminance non-uniformity occurs, sothat the light emitting characteristics cannot be satisfied adequately.Therefore, using CMP, the surface is polished to the arithmetic averageroughness Ra of less than or equal to 50 nm. While the smaller theplanarity the more preferable, such a high degree of planarity as to beless than or equal to 20 nm as shown in Patent Document 1 is notrequired. When the planarity is less than or equal to 50 nm, the colornon-uniformity and/or luminance non-uniformity does not appear to such adegree as to be problematic. The polishing is carried out by CMP thesurface of the organic insulating layer 32 while supplying, for example,a Ceria (CeO₂)-based slurry or a fumed silica-based slurry along withwater and alcohol.

Thereafter, as shown in FIG. 3D, a contact hole 30 a to reach the TFT 20is formed in the planarizing layer 30 (S4). In the same manner as thepreviously-described contact hole 24 a, forming of the contact hole 30 ais carried out using etching such as dry etching after a resist mask isformed. In a case of collectively etching layers in which an inorganicinsulating layer and an organic insulating layer co-exist, such as theplanarizing layer 30, the etching rates of both of the layers differfrom each other, so that using dry etching in particular is preferablefor making it unlikely for a stepped portion to be produced at theinterface of both of the layers. When the stepped portion is produced,the interior of the contact hole 30 a is not completely embedded withmetal, making it likely to produce the problem of the contact resistanceof the metal with the source electrode 25 increasing.

Thereafter, as shown in FIG. 3E, a metal is embedded at the interior ofthe contact hole 30 a and a first electrode 41 for the organic lightemitting element 40 is formed in a given region (S5). More specifically,using sputtering, for example, an underlayer in which are deposited anITO layer having a thickness of approximately 10 nm and an Ag layer oran APC layer having a thickness of approximately 100 nm, and anoverlayer comprising an ITO layer having a thickness of approximately 10nm are formed. As a result, a deposited layer of the ITO, the metallayer, and the ITO layer is formed on the surface of the planarizinglayer 30 as well as the ITO and metal being embedded at the interior ofthe contact hole 30 a. Thereafter, the deposited layer of the ITO, themetal and the ITO are patterned to form the first electrode 41.

Thereafter, as shown in FIG. 3F, an organic light emitting layer 43 isformed on the first electrode 41 (S6). Specifically, an insulating bank42 to prevent the cathode and the anode from being in contact with eachother as well as to demarcate each pixel is formed at the peripheraledge of the first electrode 41. The insulating bank 42 can be aninorganic insulating layer such as SiO₂, or an organic insulating layersuch as a polyimide resin or an acrylic resin. Such an insulating layeris formed on the entire surface and patterned such that a given locationof the first electrode 41 is exposed. The insulating bank 42 is formedto a height of approximately 1 μm. As described previously, whilevarious organic materials are deposited in forming of the organic lightemitting layer 43, depositing of the organic materials is carried out byvacuum vapor deposition, for example, in which case the organic lightemitting layer 43 is formed through an aperture of a vapor depositionmask, the vapor deposition mask having the aperture corresponding to adesired sub-pixel of R, G, or B. A layer such as LiF to improve theinjectability of electrons can be formed on the surface of the organiclight emitting layer 43. The organic light emitting layer 43 can also beformed by printing such as inkjet printing, not by vapor deposition. Agor APC is used in the first electrode 41 for the reason that lightemitted in the organic light emitting layer 43 is reflected for use asthe top emission type.

Thereafter, as shown in FIG. 3G, a second electrode (cathode) 44 isformed on the organic light emitting layer 43 (S7). The second electrode44 is formed by forming, on the entire surface, a thin layer of Mg—Ageutectic layer using vapor deposition, for example, to make it acathode. The second electrode 44 is formed also on the second contact 45and connected to the cathode wiring 27 via the second contact 45 and thefirst contact 28. With respect to the Mg—Ag eutectic layer, Mg and Aghave different melting points, so that Mg and Ag are evaporated fromdifferent crucibles to be eutecticized at the time of formation of theMg—Ag eutectic layer. With the Mg—Ag eutectic layer comprising Mg atapproximately 90 mass % and Ag at approximately 10 mass %, the secondelectrode 44 is formed to the thickness of approximately 10 nm to 20 nm,for example.

An encapsulation layer 46 to protect the second electrode 44 and theorganic light emitting layer 43 from moisture or oxygen is formed on theabove-mentioned second electrode 44. The encapsulation layer 46 protectsthe second electrode 44 and the organic light emitting layer 43 beingsusceptible to moisture or oxygen, so that an inorganic insulating layersuch as SiO₂ or SiN_(X) being difficult to absorb moisture is formedusing plasma CVD. Even more, the encapsulation layer 46 is formed suchthat the end portion thereof comes into close contact with an inorganiclayer such as a second inorganic insulating layer 33. This is because,while joining of the inorganic layers together causes them to be joinedin close contact with each other, it is difficult to obtain a completejoining, with an organic layer, having a good contactability. Therefore,in a case of no second inorganic insulating layer 33 shown in FIG. 1, itis preferable to remove a portion of the organic insulating layer 32 tocause the organic insulating layer 32 to be joined with the firstinorganic insulating layer being the underlayer thereof. This makes itpossible to fully prevent penetration of moisture.

Example 2

In the method of manufacturing an organic EL display apparatus accordingto Example 1 as shown in FIGS. 2A and 2B and FIGS. 3A to 3G, theplanarizing layer 30 is formed of the first inorganic insulating layer31 and the organic insulating layer 32 (a structure without the secondinorganic insulating layer 33 of the structure in FIG. 1). Even withsuch a structure, the surface of the organic insulating layer 32 ispolished and the first electrode 41 is formed on the surface thereof.Therefore, the surface of the planarizing layer 30 is planarized, sothat there are no problems. However, there is a problem that, when wetetching is carried out at the time of forming the contact hole 30 a,moisture easily penetrates the organic insulating layer 32 and, evenwhen dry etching is carried out, an etching gas easily penetrates theorganic insulating layer 32. In a case that moisture penetrates theorganic insulating layer 32, the material of the organic light emittinglayer 43 or the second electrode 44 could deteriorate when moistureleaches out at the time the light emitting element is formed and is inoperation. Therefore, the second inorganic insulating layer 33 ispreferably formed on the surface of the organic insulating layer 32, thestructure of which is shown in FIG. 1. The above-mentioned method ofmanufacturing is explained with reference to FIGS. 4A to 4E.

Up to the process shown in previously-described FIG. 3C, theabove-mentioned method is carried out in the same manner as thataccording to Example 1. In other words, the surface of the organicinsulating layer 32 is planarized using CMP. Thereafter, as shown inFIG. 4A, the second inorganic insulating layer 33 is formed by formingSiN_(X) having a thickness of approximately 200 nm using plasma CVD inthe same manner as the first inorganic insulating layer 31. The secondinorganic insulating layer 33 is formed by depositing an inorganicmaterial using a method such as plasma CVD as described previously, and,even more, it is very thin, so that the planarity of the polishedsurface of the organic insulating layer 32 is maintained as it is.Therefore, even for the surface of the second inorganic insulating layer33, the planarity being less than or equal to 50 nm in arithmeticaverage roughness Ra is obtained. In other words, while the planarizinglayer 30 is configured by the first inorganic insulating layer 31, theorganic insulating layer 32, and the second inorganic insulating layer33 in the Example 2, the surface of the planarizing layer 30 is formedto a planar surface being less than or equal to 50 nm in the arithmeticaverage roughness Ra.

While the below-described process is the same as that in thepreviously-described Example 1, as shown in FIG. 4B, the contact hole 30a is formed in the planarizing layer 30. The method for forming it isthe same as that according to Example 1, so that explanations thereofwill be omitted.

Thereafter, as shown in FIG. 4C, a metal is embedded at the interior ofthe contact hole 30 a and the first electrode 41 for the organic lightemitting element 40 is formed on the surface of the planarizing layer30. This method is also the same as the previously-described process inFIG. 3E, so that the explanation thereof will be omitted.

Thereafter, as shown in FIG. 4D, after the insulating bank 42 is formed,the organic light emitting layer 43 is formed using a method such asvacuum deposition, for example. This method is also the same as theprocess shown in FIG. 3F according to the previously-described Example1, so that explanations thereof will be omitted.

Thereafter, as shown in FIG. 4E, the second electrode 44 is formed onthe entire surface. This process is also the same as the process shownin FIG. 3G according to the previously-described Example 1, so thatforming can be carried out using the same method. Thereafter, formingthe encapsulation layer 46 on the surface allows the organic EL displayapparatus shown in FIG. 1 to be obtained.

SUMMARY

(1) An organic EL display apparatus according to one embodiment of thepresent invention comprises: a substrate having a surface on which adrive circuit comprising a thin film transistor is formed, a planarizinglayer to planarize the surface of the substrate by covering the drivecircuit, and an organic light emitting element, the organic lightemitting element comprising a first electrode being formed on a surfaceof the planarizing layer and connected to the drive circuit, an organiclight emitting layer being formed on the first electrode, and a secondelectrode being formed on the organic light emitting layer, wherein theplanarizing layer comprises a first inorganic insulating layer and anorganic insulating layer, the first inorganic insulating layer and theorganic insulating layer being deposited on the drive circuit, and asurface of the organic insulating layer is formed to less than or equalto 50 nm in arithmetic plane roughness Ra.

According to the present embodiment, the surface of the organicinsulating layer is formed to less than or equal to 50 nm in arithmeticplane roughness Ra using CMP, rather than forming a first electrode ofthe organic insulating layer with the surface of a planarizing layerbeing the surface formed in the organic insulating layer as it is, and,moreover, the organic light emitting layer is formed such that it avoidsa portion being immediately above a contact hole. As a result, even inthe microscopically planar state, there is no unevenness and the normaldirection of the surface of the organic light emitting layer of a smallsub-pixel almost matches the normal direction of the display screen. Asa result, the problem of light of some of small sub-pixels travelling inan oblique direction is eliminated, and factors decreasing the displayquality, such as luminance non-uniformity or color non-uniformity. As aresult, an organic EL display apparatus having a very good displayquality is obtained.

(2) The organic insulating layer being an acrylic resin or a polyimideresin is preferable in having the heat-resisting property and resultingin a stable insulating layer.

(3) The organic insulating layer being a non-photosensitive resin ispreferable in that it contains no photopolymerization initiator beingeasy to make the surface uneven, allowing a sufficient planarity of thesurface to be obtained.

(4) The planarizing layer having a three-layer structure in which asecond inorganic insulating layer is formed on the organic insulatinglayer is preferable in that it is easy to prevent moisture frompenetrating the organic insulating layer even at the time of forming acontact hole.

(5) A contact hole being collectively formed in the three-layerstructure is preferable in that the organic insulating layer is notexposed to the etching atmosphere and penetration of moisture into theorganic insulating layer can be suppressed.

(6) The organic light emitting element can be made to be eitherstructure of a bottom emission type light emitting element in which thethin film transistor is not formed at a region right below the organiclight emitting layer and light is extracted from the substrate end, or atop emission type light emitting element in which the thin filmtransistor is formed at a region right below the organic light emittinglayer and light is extracted from the second electrode. In other words,with either structure, the cause to reduce the display quality, such asluminance non-uniformity or color non-uniformity, due to the planarityof the planarizing layer is eliminated, allowing an organic EL displayapparatus having a very good display quality to be obtained.

(7) A method of manufacturing an organic EL display apparatus accordingto another embodiment of the present invention comprises: forming adrive circuit on a substrate, the drive circuit comprising a thin filmtransistor (TFT); forming, on a surface of the drive circuit, a firstinorganic insulating layer and an organic insulating layer; polishing asurface of the organic insulating layer by chemical mechanical polishing(CMP); forming a contact hole in the organic insulating layer and thefirst inorganic insulating layer, the contact hole to reach the TFT;embedding a metal at an interior of the contact hole and forming a firstelectrode at a given region; forming an organic light emitting layer onthe first electrode; and forming a second electrode on the organic lightemitting layer.

According to the present embodiment, the surface of an organicinsulating layer is polished by CMP, causing the surface of aplanarizing layer to be planarized even when viewed microscopically.Therefore, the color non-uniformity or luminance non-uniformity to becaused by the normal direction of the surface of the organic lightemitting layer differing from the normal direction of the displaysurface is suppressed.

(8) A second inorganic insulating layer being formed on the organicinsulating layer and the contact hole being collectively formed in athree-layer structure comprising the second inorganic insulating layer,the organic insulating layer, and the first inorganic insulating layerare preferable in not only that the process of forming a contact hole iseasy, but that an organic insulating layer is protected by an inorganicinsulating layer, so that penetration of moisture can be suppressed.

(9) It is preferable that the surface of the organic insulating layer ispolished such that the planarity thereof is brought to greater than orequal to 20 nm and less than or equal to 50 nm in arithmetic averageroughness Ra by carrying out planarizing with a neutral Ceria-basedpolishing material or a fumed silica-based slurry, along with water andalcohol, because the organic insulating layer can be planarly polished.

(10) The forming of the contact hole being carried out by dry etching ispreferable in that etching can be carried out without producing astepped portion even at the interface between the inorganic insulatinglayer and the organic insulating layer having different etching rates.When a stepped portion is produced on the interface of the inorganicinsulating layer and the organic insulating layer, a metal is notsufficiently into the contact hole, making it easy to result in anincrease in contact resistance.

-   -   10 Substrate    -   20 TFT    -   21 Semiconductor layer    -   30 Planarizing layer    -   31 First inorganic insulating layer    -   32 Organic insulating layer    -   33 Second inorganic insulating layer    -   40 Organic light emitting element    -   41 First electrode (anode)    -   43 Organic light emitting layer    -   44 Second electrode (cathode)

1. An organic EL display apparatus comprising: a substrate having a surface on which a drive circuit comprising a thin film transistor is formed, a planarizing layer including a first inorganic insulating layer and an organic insulating layer to planarize the surface of the substrate by covering the drive circuit, and an organic light emitting element, the organic light emitting element comprising a first electrode being formed on a surface of the planarizing layer and connected, via a contact formed in the planarizing layer, to the drive circuit, an organic light emitting layer being formed on the first electrode, and a second electrode being formed on the organic light emitting layer, wherein a surface of the organic insulating layer is formed such that a planarity thereof is brought to be greater than or equal to 20 nm and less than or equal to 50 nm in arithmetic average roughness Ra, and wherein the first electrode and the light emitting layer with substantially the same degree of surface roughness as that of the planarizing layer are formed on only a region of the surface of the planarizing layer, in which the contact is not formed, thereby, even in the microscopically planar state, a surface of the light emitting layer having no unevenness.
 2. The organic EL display apparatus according to claim 1, wherein the organic insulating layer is an acrylic resin or a polyimide resin.
 3. The organic EL display apparatus according to claim 1, wherein the organic insulating layer is a non-photosensitive resin.
 4. The organic EL display apparatus according to claim 1, wherein the planarizing layer has a three-layer structure in which a second inorganic insulating layer with substantially the same degree of surface roughness as that of the organic insulating layer is formed on the organic insulating layer.
 5. (canceled)
 6. The organic EL display apparatus according to claim 1, wherein the organic light emitting element is a bottom emission type light emitting element in which the thin film transistor is not formed at a region right below the organic light emitting layer and light is extracted from the substrate end, or a top emission type light emitting element in which the thin film transistor is also formed at a region right below the organic light emitting layer and light is extracted from the second electrode.
 7. A method of manufacturing an organic EL display apparatus, the method comprising: forming a drive circuit on a substrate, the drive circuit comprising a thin film transistor (TFT); forming, on a surface of the drive circuit, a first inorganic insulating layer and an organic insulating layer; polishing a surface of the organic insulating layer, by CMP, such that a planarity thereof is brought to be greater than or equal to 20 nm and less than or equal to 50 nm in arithmetic average roughness Ra; forming a contact hole in the organic insulating layer and the first inorganic insulating layer, the contact hole to reach the TFT; embedding a metal at an interior of the contact hole and forming a first electrode continuously to the metal embedded into the contact hole at a given region in which the contact hole is not formed, on a surface of the organic insulating layer, the first electrode with substantially the same degree of surface roughness as that of the organic insulating layer; forming an organic light emitting layer with substantially the same degree of surface roughness as that of the first electrode on the first electrode, a normal direction of a surface of the organic light emitting layer matching a normal direction of a display screen; and forming a second electrode on the organic light emitting layer.
 8. The method of manufacturing an organic EL display apparatus according to claim 7, wherein a second inorganic insulating layer with the same degree of surface roughness as that of the organic insulating layer is formed on the organic insulating layer and the contact hole is collectively formed in a three-layer structure comprising the second inorganic insulating layer, the organic insulating layer, and the first inorganic insulating layer.
 9. The method of manufacturing an organic EL display apparatus according to claim 7, wherein polishing, by CMP, the surface of the organic insulating layer is carried out with a neutral Ceria-based polishing material or a fumed silica-based slurry, along with water and alcohol.
 10. The method of manufacturing an organic EL display apparatus according to claim 7, wherein the forming of the contact hole is carried out by dry etching.
 11. The organic EL display apparatus according to claim 1, wherein a normal direction of the surface of the organic light emitting layer of each pixel matches a normal direction of a display screen. 